U.S. patent application number 15/074012 was filed with the patent office on 2016-07-14 for short-distance radio communication system for vehicle.
The applicant listed for this patent is Panasonic Intellectual Property Management Co., Ltd.. Invention is credited to JUN FUJIYAMA, NAOKI HAYASHI, TORU NISHIMURA, MASAMI TAKIGAWA.
Application Number | 20160205498 15/074012 |
Document ID | / |
Family ID | 52778461 |
Filed Date | 2016-07-14 |
United States Patent
Application |
20160205498 |
Kind Code |
A1 |
TAKIGAWA; MASAMI ; et
al. |
July 14, 2016 |
SHORT-DISTANCE RADIO COMMUNICATION SYSTEM FOR VEHICLE
Abstract
This short-distance radio communication system for a vehicle
includes an in-vehicle unit having more than one antenna and a
portable unit performing radio communications with the in-vehicle
unit. The in-vehicle unit transmits a first burst together with a
call signal for calling the portable unit through a first antenna,
and transmits a second burst subsequent to the first burst through
a second antenna. The portable unit receives the signals
transmitted from the in-vehicle unit, measures respective received
signal strength indicators from the first burst and the second
burst contained in the received signals, and responds to the
in-vehicle unit according to results of comparing the respective
indicators with given thresholds.
Inventors: |
TAKIGAWA; MASAMI; (Kanagawa,
JP) ; HAYASHI; NAOKI; (Kanagawa, JP) ;
FUJIYAMA; JUN; (Kanagawa, JP) ; NISHIMURA; TORU;
(Kanagawa, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Panasonic Intellectual Property Management Co., Ltd. |
Osaka |
|
JP |
|
|
Family ID: |
52778461 |
Appl. No.: |
15/074012 |
Filed: |
March 18, 2016 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP2014/004968 |
Sep 29, 2014 |
|
|
|
15074012 |
|
|
|
|
Current U.S.
Class: |
455/41.2 |
Current CPC
Class: |
H01Q 1/32 20130101; G08C
2201/91 20130101; G08C 17/02 20130101; B60R 25/245 20130101; H04W
4/80 20180201 |
International
Class: |
H04W 4/00 20060101
H04W004/00; H01Q 1/32 20060101 H01Q001/32 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 2, 2013 |
JP |
2013-207251 |
Claims
1. A short-distance radio communication system for a vehicle,
comprising: an in-vehicle unit having a plurality of antennas; and
a portable unit performing radio communications with the in-vehicle
unit, wherein the in-vehicle unit has a first antenna as an
in-vehicle antenna and a second antenna as an out-vehicle antenna,
the in-vehicle unit transmitting a first burst together with a call
signal for calling the portable unit through the first antenna, the
in-vehicle unit transmitting a second burst subsequent to the first
burst through the second antenna, and wherein the portable unit
does not respond to the call signal to the in-vehicle unit (1) if a
first received signal strength indicator measured from the first
burst does not exceed a predetermined first threshold, or (2) if
the first received signal strength indicator exceeds the
predetermined first threshold and a second received signal strength
indicator measured from the second burst exceeds a predetermined
second threshold, when the portable unit receives signals
transmitted from the in-vehicle unit, measures respective received
signal strength indicators from the first burst and the second
burst contained in the received signals, and responds to the call
signal to the in-vehicle unit according to results of comparing the
respective indicators with predetermined thresholds.
2. The short-distance radio communication system for a vehicle of
claim 1, wherein the in-vehicle unit further includes a third
antenna, which is an out-vehicle antenna different from the second
antenna, and wherein the portable unit does not respond to the call
signal to the in-vehicle unit (3) if the first received signal
strength indicator exceeds the predetermined first threshold, the
second received signal strength indicator does not exceed the
predetermined second threshold, and a third received signal
strength indicator measured from a third burst exceeds the
predetermined second threshold.
3. The short-distance radio communication system for a vehicle of
claim 2, wherein one of the second antenna and the third antenna is
an out-vehicle driver's seat door handle antenna, and the other is
an out-vehicle passenger's seat door handle antenna.
4. The short-distance radio communication system for a vehicle of
claim 1, wherein the portable unit does not respond to the call
signal to the in-vehicle unit by shifting the portable unit to a
sleep state.
5. The short-distance radio communication system for a vehicle of
claim 2, wherein the portable unit responds to the call signal to
the in-vehicle unit at least (4) if the first received signal
strength indicator exceeds the predetermined first threshold and
both of the second received signal strength indicator and the third
received signal strength indicator do not exceed the predetermined
second threshold.
Description
TECHNICAL FIELD
[0001] The present disclosure relates to a short-distance radio
communication system for a vehicle that performs short-distance
radio communications between a key carried by a user and a
vehicle.
BACKGROUND ART
[0002] In recent years, a smart entry system evolved from a keyless
entry system is achieving widespread use as a system for locking
and unlocking doors of a vehicle. A keyless entry system locks and
unlocks vehicle doors with a button provided on the key pressed,
where the key needs to be taken out from a bag or pocket for
example.
[0003] On the other hand, a smart entry system, provided with a
short-distance radio communication capability between a vehicle and
a key (referred to as a smart key hereinafter), locks and unlocks
vehicle doors by means of radio communications between the vehicle
and vehicle doors. Concretely, a user unlocks vehicle doors simply
by touching a touch sensor on the vehicle with a smart key
remaining in a bag or pocket while the vehicle doors are locked;
the user locks vehicle doors simply by touching the touch sensor
while the vehicle doors are unlocked. With a smart entry system, if
a smart key is detected inside the vehicle, the engine can be
started without the need of inserting the key into the key hole of
the vehicle. Under such circumstances, whether a smart key is
present inside or outside a vehicle needs to be properly
detected.
[0004] This smart entry system is provided with more than one
antennas on the vehicle and an antenna control unit that controls
to determine which antenna is to be used. When the antenna control
unit transmits a high-power signal to an intended antenna, a weak
signal can be accordingly sent to other antennas that must be under
no-signal conditions, a problem called crosstalk.
[0005] For example, to detect a smart key, when an antenna provided
inside a vehicle transmits a high-power signal toward the smart
key, an antenna provided outside the vehicle as well transmits a
signal that is low-power but can be detected by the smart key. At
this moment, if the smart key is present immediately near the
outside antenna, determination and positioning is made that the
smart key is present inside the vehicle. For example, in a case
where a user is outside the vehicle with their back facing a door
handle, with a smart key remaining in a rear pocket for instance,
determination is made that the smart key is inside the vehicle. In
such a state, a small child may accidentally start the engine.
[0006] To avoid such a situation, the technology disclosed in
patent literature 1 for example has been devised. Patent literature
1 discloses a technology in which, while coding signals are not
transmitted to the first antenna, a disturbing signal is
transmitted to the second antenna to turn the second antenna into
no-signal conditions.
CITATION LIST
Patent Literature
[0007] PTL 1 Japanese Patent Unexamined Publication No.
2004-129228
SUMMARY OF THE INVENTION
[0008] In the technology disclosed in above patent literature 1,
the left front door is provided with a first antenna, and the right
front door is provided with a second antenna, where these antennas
are placed apart from each other, and thus each coverage of signals
from each antenna does not overlap with the other coverage. In a
typical smart entry system, an antenna is provided inside the
vehicle and the antenna (e.g., the first antenna) inside the
vehicle and the antenna (e.g., a second antenna) on the front door
are close to each other, and thus the coverages of signals from the
antennas may overlap with each other. In such circumstances, the
antenna on the front door in no-signal conditions induces the
in-vehicle antenna to no-signal conditions in a region where signal
coverages overlap, which disables detecting a smart key present in
this region.
[0009] An object of the present disclosure is to provide a
short-distance radio communication system for a vehicle that
properly detects the position of a smart key even in a case where
crosstalk occurs between antennas.
[0010] A short-distance radio communication system for a vehicle of
the present disclosure includes an in-vehicle unit having more than
one antenna and a portable unit performing radio communications
with the in-vehicle unit. The system may have the following
configuration. That is, the in-vehicle unit transmits a first burst
together with a call signal for calling the portable unit through
the first antenna, and then transmits a second burst subsequent to
the first burst through the second antenna. The portable unit
receives the signals transmitted from the in-vehicle unit; measures
respective received signal strength indicators from the first and
second bursts contained in the received signals; and responds to
the in-vehicle unit according to results of comparing the
respective indicators with given thresholds.
[0011] A short-distance radio communication system for a vehicle of
the present disclosure includes more than one antenna provided in
an enclosed space formed of an enclosed body; a first communication
device provided in the enclosed space; and a second communication
device that is portable and performs radio communications with the
first communication device. The system may have the following
configuration. That is, the first communication device transmits a
first burst together with a call signal for calling the second
communication device through the first antenna, and then transmits
a second burst subsequent to the first burst through the second
antenna. The second communication device receives the signals
transmitted from the first communication device; measures
respective received signal strength indicators from the first and
second bursts contained in the received signals; and responds to
the first communication device according to results of comparing
the respective indicators with given thresholds.
[0012] According to the present disclosure, the position of a smart
key can be accurately detected even in a case where crosstalk
occurs between antennas.
BRIEF DESCRIPTION OF DRAWINGS
[0013] FIG. 1 illustrates the positions of antennas for smart entry
provided on a vehicle.
[0014] FIG. 2 illustrates an outline structure of a smart entry
system according to the first exemplary embodiment of the present
disclosure.
[0015] FIG. 3 illustrates signals and their timing transmitted from
each antenna by the microprocessor on the in-vehicle unit shown in
FIG. 2.
[0016] FIG. 4 is a flowchart showing the operation procedure of the
microprocessor on the smart key shown in FIG. 2.
[0017] FIG. 5 illustrates possible areas where the smart key is
present with respect to the vehicle viewed from the above.
[0018] FIG. 6 illustrates signals and their timing transmitted from
each antenna by the microprocessor on the in-vehicle unit according
to the second exemplary embodiment of the present disclosure.
[0019] FIG. 7 is a flowchart showing the operation procedure of the
microprocessor on the smart key according to the second
embodiment.
[0020] FIG. 8 illustrates possible areas where the smart key is
present with respect to the vehicle viewed from the above.
[0021] FIG. 9 illustrates signals and their timing transmitted from
each antenna by the microprocessor on the in-vehicle unit according
to the third exemplary embodiment of the present disclosure.
[0022] FIG. 10 is a flowchart showing the operation procedure of
the microprocessor on the smart key according to the third
embodiment.
[0023] FIG. 11 illustrates possible areas where the smart key is
present with respect to the vehicle viewed from the above.
DESCRIPTION OF EMBODIMENTS
[0024] Hereinafter, a detailed description is made of some
embodiments of the present disclosure in reference to the
drawings.
First Exemplary Embodiment
[0025] FIG. 1 illustrates the positions of antennas for smart entry
provided on a vehicle (enclosed body). In FIG. 1, the vehicle has
three antennas: in-vehicle front antenna (F antenna hereinafter)
111, in-vehicle middle antenna (M antenna hereinafter) 112, and
in-vehicle rear antenna (R antenna hereinafter) 113 inside the
vehicle (an enclosed space).
[0026] Outside the vehicle, three antennas are provided:
out-vehicle driver's seat door handle antenna (FRDR antenna
hereinafter) 114, out-vehicle passenger's seat door handle antenna
(FRAS antenna hereinafter) 115, and out-vehicle tail gate antenna
(TG antenna hereinafter) 116.
[0027] In the first embodiment, a description is made of a case
where the system prevents the engine from starting when a smart key
is present near FRDR antenna or FRAS antenna (i.e., outside the
vehicle). In the following description, the smart key is assumed to
be present near FRAS antenna.
[0028] FIG. 2 illustrates an outline structure of smart entry
system 100, which is a short-distance radio communication system
for a vehicle according to the first exemplary embodiment. Smart
entry system 100 includes in-vehicle unit 110 (the first
communication device) provided on the vehicle, and smart key 130
(the second communication device) carried by a user.
[0029] In-vehicle unit 110 includes multiple transmitting antennas
111 through 116, transmitting units 121 through 126, RF receiving
antenna 117, RF receiving unit 127, and in-vehicle unit
microprocessor (also referred to as an antenna control unit)
128.
[0030] Multiple transmitting antennas 111 through 116 correspond to
F antenna 111, M antenna 112, R antenna 113, FRDR antenna 114, FRAS
antenna 115, and TG antenna 116, where the first three are provided
inside the vehicle; the last three, outside.
[0031] Transmitting units 121 to 126 are respectively connected to
transmitting antennas 111 to 116, perform transmission processes
(e.g., modulation, amplification) on a signal output from
in-vehicle unit microprocessor 128, and transmit the resulting
signal through one of the transmitting antennas.
[0032] RF receiving antenna 117 receives an RF (radio frequency)
signal transmitted from smart key 130. RF receiving unit 127
performs reception processes (e.g., demodulation) on the signal
received by RF receiving antenna 117, and outputs the signal that
has undergone reception processes to in-vehicle unit microprocessor
128.
[0033] In-vehicle unit microprocessor 128 controls to determine
which one of transmitting antennas 111 to 116 is to be used, and
controls operation such as locking/unlocking of vehicle doors and
permits engine start according to results of detecting smart key
130.
[0034] Meanwhile, smart key 130 includes receiving antenna 131,
receiving unit 132, microprocessor on the smart key (smart key
microprocessor) 133, RF transmitting unit 134, and RF transmitting
antenna 135.
[0035] Receiving antenna 131 receives a signal transmitted from
each of antennas 111 through 116 of in-vehicle unit 110. Receiving
unit 132 performs reception processes (e.g., demodulation) on the
signal received through receiving antenna 131, and outputs the
signal that has undergone reception processes to smart key
microprocessor 133.
[0036] Smart key microprocessor 133 measures an RSSI (received
signal strength indicator) from a signal output from receiving unit
132; compares the RSSI measured with a given threshold (threshold
decision); and outputs an RF response to RF transmitting unit 134
according to the decision results. Detailed operation of smart key
microprocessor 133 is described later.
[0037] RF transmitting unit 134 performs transmission processes
(e.g., modulation, amplification) on the RF response output from
smart key microprocessor 133, and transmits the RF response that
has undergone transmission processes to in-vehicle unit 110 through
RF transmitting antenna 135.
[0038] FIG. 3 illustrates signals and their timing that in-vehicle
unit microprocessor 128 shown in FIG. 2 transmits through each of
antennas 111 through 116. In-vehicle unit microprocessor 128
successively transmits call signals and RSSI bursts (first burst)
through F antenna 111, M antenna 112, and R antenna 113, and at
their each timing transmits RSSI bursts (second burst) for FRDR and
FRAS. FIG. 3 illustrates circumstances when signals are transmitted
through F antenna 111 as an example. Here, a burst refers to a
radio signal transmitted for measuring a received signal strength
indicator.
[0039] In FIG. 3, a call signal contains a signal for waking up
smart key 130 in a sleep state, an ID for authenticating pairing of
in-vehicle unit 110 and smart key 130, and auxiliary bits. Here, a
sleep state refers to a state where a smart key wakes up when
receiving a call signal. Details about auxiliary bits are described
later. An RSSI burst for F antenna is a continuous signal for smart
key 130 to measure an RSSI (received signal strength indicator)
through F antenna 111. The signals of from a call signal to an RSSI
burst for F antenna are in the existing format.
[0040] Similarly, RSSI bursts for FRDR and for FRAS are continuous
signals for measuring RSSIs from each antenna.
[0041] FIG. 3 shows a case where a signal is transmitted through F
antenna 111; the situation is the same for M antenna 112 and R
antenna 113.
[0042] Smart key 130 that has received such signals measures an
RSSI from each RSSI burst; compares the RSSI measured with a given
threshold; and detects the position of smart key 130 based on the
results of the threshold decision. In this case, smart key 130 is
assumed to be present near FRAS antenna 115, and thus does not
respond to the call through F antenna 111.
[0043] Next, a description is made of auxiliary bits. The auxiliary
bits are set to "0000" in the existing format, which directs
decision of an RSSI burst for each antenna subsequent to the
auxiliary bits. In this embodiment, when auxiliary bits are "1000",
the existing format is followed by an RSSI burst for FRDR and an
RSSI burst for FRAS that are allocated direction of measuring
RSSIs. That is, the auxiliary bits contained in the call signal
shown in FIG. 3 are set to "1000".
[0044] Next, a description is made of detailed operation of smart
key microprocessor 133 shown in FIG. 2 using FIGS. 4 and 5. FIG. 4
is a flowchart showing the operation procedure of smart key
microprocessor 133. FIG. 5 illustrates possible areas where the
smart key is present with respect to the vehicle viewed from the
above.
[0045] In step ST201 of FIG. 4, smart key microprocessor 133
receives a call signal through F antenna. In step ST202,
determination is made whether or not the auxiliary bits contained
in the call signal are "1000". If not "1000" (ST202: NO), the
process proceeds to step ST203; otherwise (YES: step ST202), to
step ST207.
[0046] In step ST203, smart key microprocessor 133 determines
whether or not the auxiliary bits contained in the call signal are
"0100". If not "0100" (step ST203: NO), the process proceeds to
step ST204; otherwise (step ST203: YES), to the flowchart of FIG.
7.
[0047] In step ST204, smart key microprocessor 133 determines
whether or not the auxiliary bits contained in the call signal are
"0000". If not "0000" (step ST204: NO), the process proceeds to
ST219, and smart key 130 shifts to a sleep state. Meanwhile, if the
auxiliary bits are "0000" (step ST204: YES), the process proceeds
to step ST205.
[0048] In step ST205, smart key microprocessor 133 measures an RSSI
burst (first burst) for each in-vehicle antenna (here, F antenna
for example). In step ST206, smart key microprocessor 133
determines whether or not the RSSI from in-vehicle F antenna
exceeds given threshold F (a threshold indicating the effective
coverage of F antenna). If exceeding (step ST206: YES), the process
proceeds to step ST218; otherwise (step ST206: NO), to ST219, and
smart key 130 shifts to a sleep state.
[0049] In step ST202, if the auxiliary bits are "1000" (step ST202:
YES), smart key microprocessor 133 measures an RSSI burst for each
in-vehicle antenna (here, F antennae for example) in step ST207. At
this moment, the AD converter (hereinafter, referred to as an ADC)
is set to a 10-bit resolution and 64 averaging times.
[0050] In step ST208, smart key microprocessor 133 sets the ADC to
a 10-bit resolution and 4 averaging times. In step ST209, smart key
microprocessor 133 measures an RSSI burst (second burst) for
FRDR.
[0051] In step ST210, smart key microprocessor 133 determines
whether or not the RSSI from in-vehicle F antenna exceeds given
threshold F. If exceeding (step ST210: YES), the process proceeds
to step ST211; otherwise (step ST210: NO), smart key 130 being
assumed to be present away from the vehicle (case 1 shown in FIG.
5), the process proceeds to step ST219, and smart key 130 shifts to
a sleep state.
[0052] In step ST211, smart key microprocessor 133 determines
whether or not the RSSI from out-vehicle FRDR antenna exceeds given
threshold b. If exceeding (step ST211: YES), the process proceeds
to step ST212; otherwise, to step ST213.
[0053] In step ST212, smart key microprocessor 133 determines that
smart key 130 is present near FRDR antenna (case 2 shown in FIG.
5). The process proceeds to step ST219, and smart key 130 shifts to
a sleep state.
[0054] In step ST213, smart key microprocessor 133 sets the ADC to
a 10-bit resolution and 4 averaging times. In step ST214, smart key
microprocessor 133 measures an RSSI burst (third burst) for
FRAS.
[0055] In step ST215, smart key microprocessor 133 determines
whether or not the RSSI from in-vehicle F antenna exceeds given
threshold F. If exceeding (step ST215: YES), the process proceeds
to step ST216; otherwise (step ST215: NO), smart key 130 being
assumed to be present away from the vehicle (case 1 in FIG. 5), the
process proceeds to step ST219, and smart key 130 shifts to a sleep
state.
[0056] In step ST216, smart key microprocessor 133 determines
whether or not the RSSI from out-vehicle FRAS antenna exceeds given
threshold b (the same value as the crosstalk threshold). If
exceeding (step ST216: YES), the process proceeds to step ST217;
otherwise (step ST216: NO), to step ST218.
[0057] In step ST217, smart key microprocessor 133 determines that
smart key 130 is present near FRAS antenna (case 2' shown in FIG.
5), the process proceeds to step ST219, and smart key 130 shifts to
a sleep state.
[0058] In step ST218, smart key 130 is assumed to be present inside
the vehicle (case 4 shown in FIG. 5) and smart key microprocessor
133 transmits an RF response to the vehicle.
[0059] In this way, smart key microprocessor 133 compares an RSSI
measured from an RSSI burst for each in-vehicle antenna with given
threshold F. If this RSSI exceeds threshold F, smart key 130 is
present inside the vehicle with a high possibility. Smart key 130,
however, can be present outside the vehicle under the influence of
crosstalk. Thus, smart key microprocessor 133 compares RSSIs
measured from RSSI bursts for FRDR and for FRAS with given
threshold b. If determination has been made that an RSSI is larger
than threshold b, smart key 130 proves present near the relevant
antenna outside the vehicle. Hence, the position of a smart key can
be detected without the need of an additional hardware device.
[0060] Thus according to the first embodiment, every time the
system transmits a call signal and an RSSI burst successively
through each in-vehicle antenna, the system transmits RSSI bursts
for FRDR and for FRAS, measures an RSSI from each RSSI burst
received by the smart key, and compares the RSSI measured with a
given threshold. This allows the position of the smart key to be
accurately detected based on results of the threshold decision.
This prevents the engine from starting when the smart key is
present near FRDR antenna or FRAS antenna (i.e., outside the
vehicle). Here, the first and second bursts may be those
transmitted from three antennas freely chosen from six antennas: F
antenna 111, M antenna 112, R antenna 113, FRDR antenna 114, FRAS
antenna 115, and TG antenna 116.
Second Exemplary Embodiment
[0061] In the second exemplary embodiment, a description is made of
a case where, when a smart key as a portable unit is present near
one door antenna (FRDR or FRAS antenna), the system prevents entry
from another door. In the following description, a smart key is
assumed to be present near FRAS antenna. The smart entry system,
which is a short-distance radio communication system for a vehicle
of the second embodiment, has a configuration similar to that of
the first embodiment shown in FIG. 2, and thus a description is
made referring to FIG. 2 as required.
[0062] FIG. 6 illustrates signals and their timing that in-vehicle
unit microprocessor 128 according to the second embodiment
transmits through each antenna. In-vehicle unit 110 successively
transmits a silent direction signal and an RSSI burst from each
antenna: F antenna 111, M antenna 112, and R antenna 113, then
transmits a call signal and an RSSI burst for FRDR through FRDR
antenna 114, and further transmits an RSSI burst for FRAS through
FRAS antenna 115. The signals of from the silent direction signal
of F antenna 111 to the RSSI burst for FRDR are in the existing
format.
[0063] Smart key 130 that has received such signals, when receiving
a silent direction signal from each in-vehicle antenna, maintains a
silent state. A silent state refers to a state where a call signal
received is ignored. Then, smart key 130, when receiving a call
signal through FRDR antenna 114, measures respective RSSIs from
RSSI bursts for FRDR and for FRAS, and compares the RSSIs measured
with given thresholds to detect the position of smart key 130.
Here, smart key 130 is assumed to be present near FRAS antenna 115,
and thus smart key 130 does not respond to the call form FRDR
antenna 114.
[0064] Next, a description is made of auxiliary bits contained in
the call signal shown in FIG. 6. In this embodiment, when the
auxiliary bits are "0100", the existing format is followed by an
RSSI burst for FRAS that are allocated direction of measuring an
RSSI. That is, the auxiliary bits contained in the call signal
shown in FIG. 6 are set to "0100".
[0065] Next, a description is made of detailed operation of smart
key microprocessor 133 according to the second embodiment using
FIGS. 7 and 8. FIG. 7 is a flowchart showing the operation
procedure of smart key microprocessor 133. FIG. 8 illustrates
possible areas where the smart key is present with respect to the
vehicle viewed from the above.
[0066] In step ST301 of FIG. 7, smart key microprocessor 133
receives a call signal through FRDR antenna 114. In step ST302,
smart key microprocessor 133 determines whether or not the
auxiliary bits contained in the call signal are "0100". If not
"0100" (step ST302: NO), the process proceeds to step ST303;
otherwise (step ST302: YES), to step ST306.
[0067] In step ST303, smart key microprocessor 133 determines
whether or not the auxiliary bits contained in the call signal are
"0000". If not "0000" (step ST303: NO), the process proceeds to
ST317, and smart key 130 shifts to a sleep state. Meanwhile, if the
auxiliary bits are "0000" (step ST303: YES), the process proceeds
to step ST304.
[0068] In step ST304, smart key microprocessor 133 measures an RSSI
burst for each in-vehicle antenna (here, F antennae for example).
In step ST305, smart key microprocessor 133 determines whether or
not the RSSI from in-vehicle F antenna exceeds given threshold F (a
threshold indicating the effective coverage of F antenna). If
exceeding (step ST305: YES), the process proceeds to step ST314;
otherwise (step ST305: NO), to ST317, and smart key 130 shifts to a
sleep state.
[0069] If the auxiliary bits are "0100" (step ST302: YES) in step
ST302, smart key microprocessor 133 measures an RSSI burst for FRDR
in step ST306. At this moment, the ADC is set to a 10-bit
resolution and 64 averaging times.
[0070] In step ST307, smart key microprocessor 133 determines
whether or not the smart key is in silent. If in silent (step
ST307: YES), the process proceeds to step ST308; otherwise (step
ST307: NO), to step ST310.
[0071] In step ST308, smart key microprocessor 133 determines
whether or not an RSSI for FRDR exceeds a given crosstalk
threshold. If exceeding (step ST308: YES), smart key microprocessor
133 releases the silent state in ST309; otherwise (step ST308: NO),
the process proceeds to step ST316. In step ST309, smart key 130 is
assumed to be present near FRDR antenna 114 (case 3 shown in FIG.
8).
[0072] In step ST310, smart key microprocessor 133 measures an RSSI
burst for FRAS. In step ST311, smart key microprocessor 133
determines whether or not an RSSI for FRDR exceeds a given
threshold. If exceeding (step ST311: YES), the process proceeds to
step ST312; otherwise (step ST311: NO), smart key 130 is assumed to
be present away from the vehicle (case 1 shown in FIG. 8) and the
process proceeds to step ST317.
[0073] In step ST312, smart key microprocessor 133 determines
whether or not the RSSI for FRDR exceeds the RSSI for FRAS. If
exceeding (step ST312: YES), the process proceeds to step ST313;
otherwise (step ST312: NO), to ST315, where smart key 130 is
assumed to be present near FRAS antenna 115 (case 5 shown in FIG.
8) and the process proceeds to step ST317.
[0074] In step ST313, smart key microprocessor 133 determines that
smart key 130 is present near the FRDR antenna. In step ST314,
smart key 130 is assumed to be present near FRDR antenna 114 (case
3 shown in FIG. 8), and smart key microprocessor 133 transmits an
RF response to the vehicle.
[0075] In step ST315, smart key microprocessor 133 determines that
smart key 130 is near FRAS antenna, the process proceeds to step
ST317, and smart key 130 shifts to a sleep state.
[0076] In step ST316, smart key 130 is assumed to be present inside
the vehicle (case 4 or case 4' shown in FIG. 8), and smart key
microprocessor 133 continues silent until the end of silent. In
step ST317, smart key 130 shifts to a sleep state.
[0077] In this way, smart key microprocessor 133 compares an RSSI
measured from an RSSI burst for FRDR with a given threshold. If
this RSSI exceeds the threshold, smart key 130 is present near FRDR
antenna 114 with a high possibility. Smart key 130, however, can be
present near FRAS antenna 115 under the influence of crosstalk.
Thus, smart key microprocessor 133 compares RSSIs measured from
RSSI bursts for FRDR and for FRAS with each other. This
determination results prove that smart key 130 is present near the
antenna the RSSI of which has been determined as larger.
[0078] Thus according to the second embodiment, a call signal and
an RSSI burst for FRDR are transmitted through FRDR antenna;
further an RSSI burst for FRAS is transmitted through FRAS antenna;
and an RSSI is measured from each RSSI burst received by a smart
key for comparison between RSSIs. This allows the position of the
smart key to be accurately detected according to the comparison
results, which, when a smart key is present near one door antenna,
prevents entry from another door.
Third Exemplary Embodiment
[0079] In a short-distance radio communication system for a vehicle
according to the third exemplary embodiment, a description is made
of a case where, when a smart key as a portable unit is present
near one door antenna (FRDR or FRAS antenna), the system prevents
unlocking of the tail gate. In the following description, a smart
key is assumed to be present near FRAS antenna. The smart entry
system, which is a short-distance radio communication system for a
vehicle of the third embodiment, has a configuration similar to
that of the first embodiment shown in FIG. 2, and thus a
description is made referring to FIG. 2 as required.
[0080] FIG. 9 illustrates signals and their timing that in-vehicle
unit microprocessor 128 according to the third exemplary embodiment
transmits through each antenna. In-vehicle unit 110 successively
transmits a silent direction signal and an RSSI burst from each
antenna: F antenna 111, M antenna 112, and R antenna 113, then
transmits a call signal and an RSSI burst for TG through TG antenna
116, and further transmits an RSSI burst for FRDR through FRDR
antenna 114 and an RSSI burst for FRAS through FRAS antenna 115.
The signals of from the silent direction signal of F antenna 111 to
the RSSI burst for TG are in the existing format.
[0081] Smart key 130 that has received such signals, when receiving
a silent direction signal from each in-vehicle antenna, maintains a
silent state. Then, smart key 130, when receiving a call signal
through TG antenna 116, measures respective RSSIs from RSSI bursts
for TG, FRDR, and FRAS, and compares the RSSIs measured with given
thresholds to detect the position of smart key 130. Here, smart key
130 is assumed to be present near FRAS antenna 115, and thus smart
key 130 does not respond to the call from TG antenna 116.
[0082] Note that the auxiliary bits contained in the call signal
shown in FIG. 9 are the same as those of the first embodiment. When
the auxiliary bits are "1000", the existing format is followed by
RSSI bursts for FRDR and FRAS that are allocated direction of
measuring RSSIs.
[0083] Next, a description is made of detailed operation of smart
key microprocessor 133 according to the third embodiment using
FIGS. 10 and 11. FIG. 10 is a flowchart showing the operation
procedure of smart key microprocessor 133. FIG. 11 illustrates
possible areas where the smart key is present with respect to the
vehicle viewed from the above.
[0084] In step ST401 in FIG. 10, smart key microprocessor 133
receives a call signal from the TG antenna. In step ST402, smart
key microprocessor 133 determines whether or not the auxiliary bits
contained in the call signal are "1000". If not "1000" (step ST402:
NO), the process proceeds to step ST403.
[0085] In step ST403, smart key microprocessor 133 determines
whether or not the auxiliary bits contained in the call signal are
"0100". If not "0100" (step ST403: NO), the process proceeds to
ST404; otherwise (step ST403: YES), to the flowchart of FIG. 7.
[0086] In step ST404, smart key microprocessor 133 determines
whether or not the auxiliary bits contained in the call signal are
"0000". If not "0000" (step ST404: NO), the process proceeds to
ST423, and smart key 130 shifts to a sleep state. Meanwhile, if the
auxiliary bits are "0000" (step ST404: YES), the process proceeds
to step ST405.
[0087] In step ST405, smart key microprocessor 133 measures an RSSI
burst for TG. In step ST406, smart key microprocessor 133
determines whether or not the RSSI from TG antenna exceeds given
threshold TG (a threshold indicating the effective coverage of TG
antenna). If exceeding (step ST406: YES), the process proceeds to
step ST421; otherwise (step ST406: NO), to step ST423, and smart
key 130 shifts to a sleep state.
[0088] In step ST402, if the auxiliary bits are "1000" (step ST402:
YES), smart key microprocessor 133 measures an RSSI burst for TG in
step ST407. At this moment, the ADC is set to a 10-bit resolution
and 64 averaging times.
[0089] In step ST408, smart key microprocessor 133 determines
whether or not the smart key is in silent. If in silent (step
ST408: YES), the process proceeds to step ST409; otherwise (step
ST408: NO), to step ST411.
[0090] In step ST409, smart key microprocessor 133 determines
whether or not the RSSI for TG exceeds a given crosstalk threshold.
If exceeding (step ST409: YES), smart key microprocessor 133
releases the silent state in ST410; otherwise (step ST409: NO), the
process proceeds to step ST422. In ST410, smart key 130 is assumed
to be present near the TG antenna (case 5 shown in FIG. 11), near
the FRDR antenna (case 2), or near FRAS antenna (case 2').
[0091] In step ST411, smart key microprocessor 133 sets the ADC to
a 10-bit resolution and 4 averaging times. In step ST412, smart key
microprocessor 133 measures an RSSI burst for FRDR.
[0092] In step ST413, smart key microprocessor 133 determines
whether or not the RSSI for TG exceeds given threshold TG. If
exceeding (step ST413: YES), the process proceeds to step ST414;
otherwise (step ST413: NO), to step ST423, where smart key 130 is
assumed to be present away from the vehicle (case 1 shown in FIG.
11).
[0093] In step ST414, smart key microprocessor 133 determines
whether or not the RSSI for FRDR exceeds given threshold b. If
exceeding (step ST414: YES), the process proceeds to step ST415;
otherwise (step ST414: NO), to step ST416.
[0094] In step ST415, smart key microprocessor 133 determines that
smart key 130 is present near FRDR antenna (case 2), the process
proceeds to step ST423, and smart key 130 shifts to a sleep
state.
[0095] In step ST416, smart key microprocessor 133 sets the ADC to
a 10-bit resolution and 4 averaging times. In step ST417, smart key
microprocessor 133 measures an RSSI burst for FRAS.
[0096] In step ST418, smart key microprocessor 133 determines
whether or not the RSSI for TG exceeds given threshold TG. If
exceeding (step ST418: YES), the process proceeds to step ST419;
otherwise (step ST418: NO), to step ST423, and smart key 130 shifts
to a sleep state.
[0097] In step ST419, smart key microprocessor 133 determines
whether or not the RSSI for FRAS exceeds given threshold b. If
exceeding (step ST419: YES), the process proceeds to step ST420;
otherwise (step ST419: NO), to step ST421.
[0098] In step ST420, smart key microprocessor 133 determines that
smart key 130 is present near FRAS antenna 115 (case 2'), the
process proceeds to step ST423, and smart key 130 shifts to a sleep
state.
[0099] In step ST421, smart key 130 is assumed to be present near
TG antenna (case 4 or case 5 shown in FIG. 11), and smart key
microprocessor 133 transmits an RF response to the vehicle.
[0100] In step ST422, smart key 130 is assumed to be present inside
the vehicle (case 3 or case 3' shown in FIG. 11), and smart key
microprocessor 133 continues silent until the end of silent. In
step ST423, smart key 130 shifts to a sleep state.
[0101] In this way, smart key microprocessor 133 compares an RSSI
measured from an RSSI burst for TG with given threshold TG. If this
RSSI exceeds threshold TG, smart key 130 is present near the tail
gate with a high possibility. Smart key 130, however, can be
present at another position under the influence of crosstalk. Thus,
smart key microprocessor 133 compares RSSIs measured from RSSI
bursts for FRDR and for FRAS with given threshold b. If
determination has been made that an RSSI is larger than threshold
b, smart key 130 is present near the relevant antenna outside the
vehicle.
[0102] Thus according to the third embodiment, a call signal and an
RSSI burst for TG are transmitted through TG antenna, RSSI bursts
for FRDR and FRAS are further transmitted, and an RSSI is measured
from each RSSI burst received by a smart key for comparison between
RSSIs and given thresholds. This allows the position of the smart
key to be accurately detected according to the comparison results,
which, when the smart key is present near one door antenna (FRDR or
FRAS antenna), prevents unlocking of the tail gate.
[0103] Note that this embodiment can be applied even in the
following case. That is, a silent direction signal from each
in-vehicle antenna leaks from FRDR antenna 114 or FRAS antenna 115,
and smart key 130 positioned near FRAS antenna 115 shifts to a
silent state. Further, a call signal from TG antenna 116 leaks from
FRDR antenna 114 or FRAS antenna 115, and the silent state of smart
key 130 is released.
[0104] All of the above completes the description of the
embodiments.
[0105] In the above embodiments, the name smart key is used; a
smart key is called otherwise, such as a fob key, electronic key,
mobile key, and badge.
[0106] In the above embodiments, the description is made assuming
that smart key microprocessor 133 performs RSSI measurement,
threshold comparison, for example. However, the following operation
may be performed. That is, smart key microprocessor 133 measures an
RSSI and transmits the RSSI to in-vehicle unit microprocessor 128,
which performs threshold comparison.
INDUSTRIAL APPLICABILITY
[0107] A short-distance radio communication system for a vehicle
according to the present disclosure is useful for detecting the
position of a smart key.
REFERENCE MARKS IN THE DRAWINGS
[0108] 100 smart entry system (short-distance radio communication
system for a vehicle) [0109] 110 in-vehicle unit (first
communication device) [0110] 111 F antenna [0111] 112 M antenna
[0112] 113 R antenna [0113] 114 FRDR antenna [0114] 115 FRAS
antenna [0115] 116 TG antenna [0116] 117 RF receiving antenna
[0117] 121 through 126 transmitting unit [0118] 127 RF receiving
unit [0119] 128 in-vehicle unit microprocessor [0120] 130 smart key
(portable unit, second communication device) [0121] 131 receiving
antenna [0122] 132 receiving unit [0123] 133 microprocessor on the
smart key [0124] 134 RF transmitting unit [0125] 135 RF
transmitting antenna
* * * * *